The present invention is directed to semiconductor packaging and, more particularly, to a method of forming pillar bumps on a chip bonding and a capillary for forming same.
Wire bond stud bumping has been used as a low cost method to replace C4 solder bumping or copper pillars in low end System in Package chip-to-chip bonding. Wire bonded studs are typically made using conventional capillary designs which yield studs in the shape of bonded balls with short tails. An aspect ratio of the stud (i.e., ratio of height to diameter) is typically less than 1. Following coining/flattening procedures, the stud heights are further reduced. As with any chip-to-chip bonding process, low stud heights lead to low bonding integrity and reliability.
To increase bump heights using conventional capillaries, the bonded ball diameters must be increased. However, to accommodate the increase, pad sizes and pitch must also be increased, which can be an issue for devices requiring a fine pitch.
It is therefore desirable to provide a method for providing higher pillar bumps that are also narrow enough to support fine pitch devices. It is further desirable to provide a capillary for use with the method.